This invention relates to a railway or tramway rail fastening system including a rail and a shell for holding a railway or tramway rail.
Great Britain application 2,272,011 (May 4, 1994) discloses a tramway rail which is secured in place by a split shell containing an infill.
According to one aspect of the present invention, there is provided a railway or tramway fastening system, comprising a shell and a resilient fill within the shell for holding a railway or tramway rail having a head, a web and a base region and the shall having an inner profile of open channel form to receive the rail, the inner profile of the shell at its upper, open side and at its lower base side being shaped to hold firmly, through the fill the head and base region, respectively, of the rail; characterized in that the inner profile of the shell between the base and the open side is narrowed so as to form a detent or pinch point through which a region of the rail has to be passed upon insertion of the rail into the shell to retain the rail.
According to a second aspect of the present invention, there is provided a railway or tramway fastening system, comprising a shell and a resilient fill within the shell for holding a railway or tramway rail of substantially symmetrical form having head and base portions joined by an intermediate portion of greater girth, the shell having an inner profile of open channel form to receive the rail and the inner profile of the shell intermediate its upper, open side and its lower, base side being shaped to hold firmly through the fill, the intermediate portion of the rail; characterized in that the inner profile of the shell between its base and the open side is narrowed so as to form a detent or pinch point through which a region of the rail has to be passed upon insertion of the rail into the shell to retain the rail.
The fill can be of stiff and strong but resilient material such as an elastomer. The fill can be bonded to the shell and/or to the rail or can be provided as a sheet for forcing into the shell upon insertion of the rail or can be poured, cast or sprayed into the space between the shell and rail.
The inner profile of the shell can be straight or curved in the lengthwise direction thereof to match a given longitudinal or vertical straightness or curvature respectively of the rail to be held in the shell.
The inner profile of the shell can be pre-profiled to match the given longitudinal straightness or curvature of the rail to be held in the shell. This pre-profiling can be achieved by applying bending forces to the shell, which forces can be applied within the inner profile and/or against the exterior of the shell.
The material of the shell is preferably stiffer than the elastomer inside it and can be of sheet material or pulltruded, extruded, moulded or cast, for example of polymer concrete, sheet metal, fibre-reinforced thermosetting resin or of fibre-reinforced thermoplastics.
The rail itself could be used to provide the required support and bending forces to the shell. Alternatively, individual formers, e.g. short lengths of rail or rail profiled material, can be located inside and/or outside of the shell to provide the required bending forces and alignment during installation.
Preferably, the shell is laid and/or set in a supporting bed or slab of, for example, concrete or asphalt.
A railway or tramway track will comprise two such shells located side-by-side and can be formed as a unified slab construction. Alternatively, the two shells can have a tie piece between them.
According to a third aspect of the present invention, there is provided a railway or tramway rail fastening system including at least one shell with resilient fill, the or each shell being essentially as defined according to the first or second aspect of the invention and the or each shell having a rail held firmly therein by the combination of fill and shell.
The rail may be substantially symmetrical in cross section so that when its head becomes worn the rail can be removed from the shell, inverted and replaced in the shell to provide a second head for use. The two rails of a track can also be changed over one for the other.
According to a fourth aspect of the present invention, there is provided a method of laying a railway or tramway rail using a shell with resilient fill essentially as defined according to the first or second aspect of the invention and causing a rail to be held firmly therein, the rail being held securely in position by the combination of fill and shell.
According to a fifth aspect of the present invention, there is provided a railway or tramway rail, the rail having a longitudinal profile including a bulged portion when viewed in cross-section, said bulged portion acting as a detent when inserted into a surrounding fastening system essentially as defined according to the first or second aspect of the invention to hold the rail in place.
The bulged portion may be in intermediate upper and lower regions of the rail or the bulged portion may be in a lower and/or upper region of the rail. This enables ease of rail replacement with minimum disruption to the remainder of the system.
The overall cross-section of the rail maybe substantially rectangular and the sides of the rail maybe provided with not just one bulged portion but two or three bulged portions, extending from the head of the rail towards its base, so as to provide a ribbed formation along the sides of the rail. With such a configuration, a webless and/or footless rail is effectively produced, thereby allowing more side wear allowance and less frequent rail change, whilst reducing corrosion sensitivity and stresses within the rail.
This comparatively simple cross-section with no web allows ultrasonic testing of the whole rail in a satisfactory manner and not just the head of the rail as at present. This is intended to avoid checking delays by identifying flaws before they cause an unplanned delay.
Such a cross-section is also intended to reduce sensitivity to inherent or load-generated defects or manufacturing defects such as inclusions and fractures. In addition, the comparatively wide head provides a greater bearing area for the wheel and the wider, and therefore more solid, webless cross-section permits sliding expansion joints to be more robust.
Finally, it is well known that noise is generated by passage of the trains on webbed rails and with the proposed cross-section, the webless rail is expected significantly to reduce noise output.
In a further development, at least one seal in the form of an elastomeric strip may be wedged between the shell and the rail in a region where there is no fill in order to give further support to the rail.